Stoker



May 16, 1944- H. v. s'ruR-rsvANT 2,348,762

STOKER Filed De. 29, 1938 Claims.

The present invention relates to stokers and more particularly to stokers of the moving grate type having automatic fuel and air supply control mechanisms for obtaining the proper combustion of fuel, and is an improvement on that type shown in my copending application, Serial No. 67,377, filed March 5, 1936.

In stokers of this type heretofore constructed, the proportions of air and fuel have been maintained in accordance with a predetermined setting for a particular grade or kind of fuel and no provision made for regulating the supply of air in accordance with varying conditions of the fuel bed due to any irregularities in kind or condition of the fuel supplied.

Regardless of the kind of fuel supplied to the Stroker, whether it be anthracite or bituminous coal, and the grate is of the underfeed or overfeed type, the condition of the fuel bed at the fire-line is a very dependable guide as to the burning characteristics or qualities of the fuel, and an important object of the present invention is to provide a novel automatic fuel bed agitating device which shall tamp the fuel bed and eiect regulation of the air supply in accordance with the temperature of different portions 0f the fuel bed in the fire-line region.

Another object of the invention is to provide a stoker air control mechanism of the character designated including a temperature responsive device having a heat transmitting member positioned adjacent the fuel bed and connected with a heat responsive member located remotely from the fuel bed. .L

Another object of the invention is to provide a control device of the character` designated in which thefheat transmitting member shall also serve as tamper for the compacting of the fuel bed at the marginal portions thereof and sealing the same against uneven distribution of air.

Another object f the invention is t0 provide a control device of the character designated having an interconnected fuel bed tamper and temperature responsive device which shall regulate the supply of air to the fuel bed in response to the temperature of that portion of the fuel bed engaged by the tamper atV any particular time.

Another object of the invention is to pI'OVide an air control mechanism of the character desianated which shall be operated by the temperature of the fuel bed as exhibited by a fluid medium passing through the fuel bed tamper and a temperature responsive device communicating therewith.

A further object of the invention is to provide an automatic regulator of the character designated which shall be durable and rugged in construction to withstand the severe heat to Awhich it is subjected, and be reliable and positive in operation to regulate the supply of air to produce the most economical combustion of fuel supplied to the fuel bed.

These and other objects of the invention will be more manifest from the following specification and drawings and more particularly set forth in the claims.

In the drawing:

Figure 1 is' a pian view of a stoker air control apparatus embodying the present invention;

Figure 2 is a view in elevation of the apparatus shown in Figure 1;

Figure 3 is an enlarged plan view of the tamper and mounting therefor; and

Figure 4 is a sectional view on line of Figure 3.

Referring to the drawing there is shown in Figures 1 and 2 an automatic stoker air regulator mechanism constructed and arranged in accordance with the present invention.

In this illustrated. embodiment of the invention fuel and air is supplied to the fuel bed of an underfeed Stoker furnace indicated by the numeral In. The fuel bed is supported on a rotary grate II to which fuel and air is supplied by conduits I2 and i3 respectively. Associated with the conduit i2 is a feed hopper I6 and a con-v veyor screw I5 for delivering fuel to the fuel bed in the usual manner as well known in the art. Connected to the air conduit I3 is a sup-- ply fan I6 arranged to deliver air to the rotary grate at any desired predetermined rate. The power connections for operating the conveyor I5 and fan I8 are not shown for they may be of any of the usual and well known motor type and no further showing is believed necessary.

'I'he grate Ii may be moved or rotated in any suitable manner, either continuously or with an intermittent movement and in this particular embodiment of the invention, the grate is'rotated by a pivoted ratchet mechanism Il, connecting rod I8, and power mechanism indicated by crank arm I9 for reciprocating the lever arm I8. The ratchet I'I engages suitable notches 28 on the grate II whereby the grate is progressively rotated with an intermittent movement.

Located adjacent to the rotary grate and overlying a radial portionof the fuel bed is a hollow tamper bar 2i. This bar is pivotally mounted on a hollow base'22 and communicating with the air conduit I3 so that a circulation of air shall be maintained therein as hereinafter more fully described.

The tamper is actuated by a crank arm 23 connected to the grate operating rod I8 so that it shall be intermittently operated simultaneously therewith and in the same directional movement so as to provide a rest period to prevent dragging on the fuel bed as hereinafter more fully described. Connected With the interior of the tamper 2i is a conduit 24 having an outlet member which is substantially bell-shaped and open to the atmosphere so as to accommodate or enclose a heat responsive device 26. This heat responsive device is preferably of the expansible uid type in which the forward end of the expansible bellows 26 is mounted in the casing 25 by a suitable support (not shown) and the free end is connected to a damper 21 located in the air delivery conduit of the fan I6. More particularly, the heat responsive device includes the rigid outlet member which is substantially bell shaped to serve as an open ended housing for directing the heated air over the bellows member 26 as it is exhausted from the hollow tamper member. This outlet member 25 is a part of the temperature responsive device and includes the bellows member 26 having one end mounted therein and the other end connected to the tamper regulator 21 to move the same yin accordance with temperature variations. The

connection is by a rod 28, and crank arm 29 upon which the damper 21 is mounted. Thus it will be observed that the desired regulation is effected by the heated air flowing through the tamper outlet pipe 24 and housing25 and over and around'the bellows member 26 to` effect the desired movement of the regulator rod 28 connected thereto.

The amount of damper opening for regulating the supply of air for any particular type of fuel is controlled by a turn buckle adjustment device 30 located in the rod connection 28.

The specific arrangement for circulating a cooling medium through the tamper bar and utilizing the resultant heat to operate the temperature responsive device 26 includes an air admission port 3i in the axle of the tamper. The port 3| is supplied by air from the conduit I3.

I Located in the tamper bar is an internal tube 32 which communicates with conduit 24 to conduct air from the tamper to the temperature responsive device 2B. From the foregoing arrangement, it will be noted that the air rst passes through the tamper receiving heat therefrom and then transmitting the heat to the heat responsive device 26 so that this device shall always be actuated in response to the temperature changes as exhibited by the tamper. It will thus be observed that the heat transmitter is placed directly in contact with the fuel bed and operates in the region ofr the fire-line indicated by the letter X."

Having thus described novel control apparatus constructed and arranged in accordance with the present invention, the operation is as follows: Assuming that the stoker fuel and air feeding devices i5 and i6 are set to maintain a desired condition of fuel bed. The rotary grate Il is moved with intermittent motion and during this movement the tamper 2l is simultaneously operated to intermittently engage a radial or peripheral portion of the fuel bed and compacts the same to seal up any air holes or cracks that may appear therein. Such cracks frequently result from an uneven combustion of fuel due to non-uniformity in grade or quality of the fuel. As the tamper is in the zone of direct heat, the air circulated therethrough serves as a cooling medium for the tamper and a. medium to transmit heat from the tamper to the damper actuator 26. By thus connecting the tamper 21 and heat responsive device 26 for actuating the same, any variation in the heat transmitted will affect the heat responsive device 26 to change or adjust the damper 21 to regulate the flow of air in accordance with the condition of the fire.

Furthermore, by providing the tamper with a yieldable coil spring operating crank arm 23, the tamper is able to compact and agitate fuel beds of varying thickness with equal facility. The adjustable connection 30 in the damper operating rod 28 provides for varying the initial position of the damper for any particular grade `or kind of fuel. These operating connections provide for a wide range of stoker operation and control in that the tamper yieldably strikes the fuel bed with an intermittent whipping motion to tamp the fuel bed without dragging and compensate for any unevenness of the fuel distribution. The amount of damper opening may be adjusted independently of the tamper operation by the adjusting device 30.

This novel apparatus constructed in accordance with my invention provides an accurate and effective control for the air supply in that it responds directly to the temperature or heat condition of the fuel bed at any particular time.

For example, should the tamper be operating in contactl with an ash portion of the fuel bed, or a portion that has burned thin, there is necessarily a dimunition of heat in this area and the tamper will be relatively cool with a result that the temperature responsive device will be actuated to supply less air so that the quantity of air supplied to the fuel `bed in relation to the fuel supplied, shall be reduced. Furthermore,v in the operation of Stoker furnaces, the position of the ash or fire line on the grate has been found to be a dependable indicator as to whether or not the correct amount of air is being supplied i or the particular resistance to flow of air which may exist in the fuel bed. For example, when the fire line or ash line works up toward the center of the fuel bed so that the fire is reduced in size, then too much air is being supplied to the fuel bed in proportion to the amount of fuel supplied. When lthe fire line recedes or approaches the peripheral edge of the burner so that the nre increases in size and discharges unburned fuel into the ash pit, then not enough air is being supplied and the rate of air feed must be increased to obtain the desired proper combustion condition.

Therefore the position of thefire line is used as the controlling influence in regulating the supply of air so that no matter what influence tends to change the resistance of the fuel bed to the flow of air, a control obtained from the position of the re line' relative to a heat receiver or transmitter would in any case maintain the proper amount of air. variations in burning qualities of the fuel or changes in rate at which fuel is fed are all compensated for either singly or in combination, by a fire line control embodying my invention.

Another feature of the improved apparatus is the reduction of fly ash. In stoker apparatus heretofore employed, after the burner has been shut down for a period 0f time, there is more ash Changes in size of fuel, y

present due to the action of natural draft during the shut down period. When the stoker is again started, there is less resistance in the fuel bed and this diminished resistance permits an excessive amount of air to blow through the fuel bed and causes a very dusty condition in the boiler resulting in blocking of the ue passages. In the device described, during a shut down period'of the burnerthe tamper becomes relatively cool and thereby causes the damper 21 to close and effect a throttling or diminution of the air supply and thereby reduce to a minimum any deleterious effects of ily ash.

Having fully described my said invention what I claim as new and desire to secure by Letters Patent is:

1. In a Stoker furnace having a movable fuel bed, means for supplying air to said fuel bed...

means for regulating the supply of air including a hollow uid receiving member positioned adjacent to and adapted to periodically contact the fuel bed, a temperature responsive means, a regulator member in said air supply and connected directly to said temperature responsive means, and means for circulating a fluid through said hollow member and then through said temperature responsive means whereby the regulator is actuated in response to the temperature of that portion of said fuel bed adjacent to the fluid receiving member.

2. Apparatus of the character described in claim 1 in which the fluid receiving member ismovable to intermittently engage a peripheral portion of the fuel bed to seal the same and prevent the formation of air holes therein.

3. In a stoker furnace,` having a rotary fuel bed, a hollow tamper mem-ber for compacting the peripheral edge portion of the fuel bed to contlnuously seal the fuel bed by intermittent tamping during the rotary movement thereof, means for supplying air to said fuel bed, temperature responsive means for regulating the supply of air, and means for circulating a fluid medium through said tamper to cool the same and then conducting the fluid to energize the heat responsive device whereby the air supply is regulated in response to the temperature of the fuel becl as exhibited by the tamper member.

4. In a stoker furnace, the combination of a movable rotary grate, means for supplying fuel and air to said grate, a hollow tamper member intermittently contacting the f'ull bed surface for compacting the fuel bed at the marginal portions of the gate, temperature responsive means for regulating'the supply of air to said yfuel bed, and

meansffor circulating a fluid medium through the tamper and then through the temperature responsive means whereby the air supply is regulated in response to the temperature exhibited by the tamper.

5. In a stoker furnace having a rotary fuel bed, means for tamping the fuel bed surface during the progressive movement thereof, means for supplying air t'o said fuel bed, temperature responsive means for regulating the supply of air, and means for circulating a fluid medium through said tamper and then through said temperature responsive means whereby the air supply to said fuel bed is regulated in response to the temperature of said tamper.

6. Apparatus of the character described in claim 5 wherein the tamping means includes a hollow tamper member extending radially of the fuel bed and adapted to engage only a small portion of the fuel bed, and means for intermittently operating the tamper.

'7. In 'a furnace having an underfeed rotary fuel bed, means for supplying air to said fuel bed, a hollow tamper bar extending radially oi said bed for tamping radial surface portions of said bed, temperature responsive means for regulating the supply of air to said bed, and means for circulating a fluid medium through said tamper and then through said temperature responsive means whereby the temperature responsive means is actuated in response to the tem perature of said tamper.

8. In a stoker furnace having a movable fuel bed, means for supplying air and fuel to said bed, means for regulating the air supply including a damper regulator, a heat transmitting tamper device positioned adjacent to the fuel bed and movable relative thereto, means for effecting a relative periodic movement between the tamper and the fuel bed, a heat responsive device associated with the heat transmitter subject to the tempera ture of said heat transmitter and means for con necting said heat responsive device to the regun lator in said air supply.

9. Apparatus of the character described in claim 8 including means for progressively movingv the fuel bed and imparting an intermittent movement to said heat transmitting device. v

10. Apparatus of the character described in claim 8 including means for imparting an intermittent movement to said fuel bed and said heat transmitting device whereby the heat transmitter shall engage the fuel bed at positions of rest during the intermittent movement.

HAROLD V. STURTEVANT. 

